1. Field of the Invention
The present invention relates to a receiver that receives radio-frequency (RF) signals.
2. Background Art
Japanese Patent Unexamined Publication No. 2005-130279 discloses a conventional receiver for diversity reception.
Hereinafter, a description is provided of a receiver for diversity reception, with reference to FIG. 4. In FIG. 4, receiver 101 includes first filter 103 for passing signals in a first frequency band, and second filter 104 for passing signals in a second frequency band, both connected on the output side of first antenna 102 in parallel with each other. Receiver 101 includes switch 131 for switching the signals in the first frequency band from first filter 103 and the signals in the second frequency band from second filter 104. Receiver 101 further includes first receiver part 109 having one input terminal connected to the output side of switch 131, and the other input terminal connected to the output side of second antenna 105, and second receiver part 110 connected to the output side of third antenna 107. Receiver 101 also synthesizes the signals in a third frequency band from second antenna 105 and the signals in the third frequency band from third antenna 107 in demodulator 111, using first receiver part 109 and second receiver part 110, for diversity reception. Demodulator 111 includes first demodulator part 123 connected on the output side of first receiver part 109, and second demodulator 124 connected on the output side of second receiver part 110. Synthesizer 133 makes diversity synthesis of the respective demodulated signals.
Receiver 101 includes a channel selector (not shown). When the signals in the first frequency band are selected, the channel selector changes switch 131 to the side of first filter 103, allowing first receiver part 109 to receive the signals in the first frequency band. When the signals in the second frequency band are selected, the channel selector changes switch 131 to the side of second filter 104, allowing first receiver part 109 to receive the signals in the second frequency band. Further, when the signals in the third frequency band are selected, the channel selector allows first receiver part 109 and second receiver part 110 to make diversity reception of the signals in the third frequency band.
However, conventional receiver 101 has switch 131 for changing the channel between first antenna 102 and first receiver part 109, and the received signals are decreased (lost) in switch 131. For this reason, the level of the signals received from first antenna 102 decreases in the input terminals of first receiver part 109 and second receiver part 110; thus the reception sensitivity deteriorates.